1. Field of Invention
The present invention relates to a packaging design for light emitting diode (LED). More particularly, the present invention relates to a light emitting diode package design that packs two or more LED dies inside the same LED package.
2. Description of Related Art
Light emitting diode (LED) is a junction diode formed by an epitaxial P-type layer and an epitaxial N-type layer on a heavily doped semiconductor compound base. The diode further includes an ohmic metallic contact on the P-type and N-type layers. In general, an LED is formed by first growing the necessary epitaxial layers on a heavily doped semiconductor compound base, and then forming ohmic metallic contacts on the P-type and N-type layers respectively. Thereafter, the die is diced out, fixed onto a panel base, wire-bonded, and then sealed by an epoxy packaging. There are several epitaxial growth methods for forming the epitaxial layer. They include the liquid crystal epitaxial growth method, the vapor phase epitaxial growth method, the metal-organic chemical vapor epitaxial growth method and the molecular beam epitaxial growth method. In addition, for forming a blue LED, an epitaxial layer is grown on an aluminum oxide/sapphire base instead.
LED is mainly packaged within an epoxy or a metallic housing. Visible LED are generally used in display screens, automobile braking lights, scanners, indicator lights for equipment and so on. At present, various colors can be generated according to the type of epitaxial layer formed in the LED die, which includes blue, red, orange, green, yellow and yellowish-green. Therefore, a multi-colored display screen formed by a collection of LEDs is available in the market nowadays.
Most conventional LEDs are packaged such that light emitted from the LED is uni-directional. In other words, the LEDs has such a narrow light-emitting angle that any display screens formed by the LEDs will have a small viewing angle beyond which one can hardly see. Therefore, conventional LEDs are unsuitable for illumination. In addition, when the distance between the viewer and the screen is too short, any images on the screen such as numbers, words or pictures will become so blurred that nothing seems to be discernible because the side of the LED emits rather poorly.
In light of the foregoing, there is a need to improve the packaging design of an LED.